We all know smoking is hazardous to our health, but this is ridiculous. An Air China jet recently dropped 21,000 feet because the co-pilot was smoking an e cigarette in the cockpit. The BBC reports, he tried to turn a fan off, meaning to prevent smoke from entering the passenger cabin. The co-pilot accidentally turned the air conditioning off instead. The resulting loss of cabin pressure resulted in the release of oxygen masks, and a rapid 21,000 foot descent. The aircraft returned to cruising altitude once cabin pressure was restored. This was reportedly not an isolated incident. There have been multiple complaints of crew member smoking onboard Air China flights.